JPH07263807A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To prevent the leakage of electromagnetic wave without increasing the number of parts by disposing a flexible printed wiring board for interconnecting a high-frequency superimposing unit and a printed wiring board so as to surround the high-frequency superimposing unit. CONSTITUTION:A semiconductor laser 1 is mounted on a high-frequency superimposing unit 2 for pulsatingly driving the semiconductor laser 1 to emit light in a multi-mode. One end of a flexible printed wiring board (FPC) 3 is fixed to a connector pin 5 provided in the shield plate of the high-frequency superimposing unit 2 by solder or the like. The FPC 3 has the width nearly equal to that of the high-frequency superimposed unit 2 and is disposed so as to surround the high-frequency superimposing unit 2, namely, in a lateral U form, and the other end is connected to a printed wiring board 4. A semiconductor laser device circuit and the like are mounted on the printed wiring board 4. Thereby, noise radiated from the high-frequency superimposed unit 2 can be reduced without increasing the number of parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device having a high frequency superimposing unit used in an optical disk device.

[0002]

2. Description of the Related Art In an optical disk device, a light beam from a semiconductor laser is narrowed down to the diffraction limit of light by an objective lens, a minute spot of about 1 μm is formed on the optical disk, and the reflected light is guided to a detection optical system for optical detection. The signal is detected by the instrument and information is obtained.

By the way, in the optical disk device, the reflected light reflected by the optical disk is returned to the semiconductor laser due to its structure, and so-called return light is generated. Particularly in a magneto-optical disk device, this return light cannot be set to 0 due to its configuration, and the generation of this return light causes a disorder in the mode of the semiconductor laser, which causes a problem that noise occurs in the signal.

In order to prevent this, it is common practice to make the semiconductor laser emit light in pulses at high frequencies (high frequency superposition). This high frequency superposition usually has a frequency of several hundred MHz,
The degree of modulation is several hundred percent. Therefore, the high-frequency component is generated as an electromagnetic wave from the current flowing through the high-frequency generation circuit that superimposes the high-frequency component on the direct current, and this electromagnetic wave becomes noise and adversely affects other electric circuits. As a countermeasure against this, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-227585, a method of covering the electromagnetic wave generated by covering the high frequency generation circuit with a shield plate has been proposed.

[0005]

However, in the above-mentioned configuration of the prior art, since the shield plate is fixed by screwing or the like, electrical contact is not sufficient and the energy of electromagnetic waves generated is large. , Electromagnetic wave leakage occurs.

The present invention provides a semiconductor laser device which prevents leakage of electromagnetic waves without increasing the number of parts.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to achieve the above object, and includes a semiconductor laser, a high frequency superimposing unit for emitting the semiconductor laser at a high frequency, and the semiconductor laser and the high frequency superimposing unit. In a semiconductor laser device comprising a PCB on which a drive circuit for driving is mounted and an FPC (flexible printed wiring board) connecting the high frequency superposition unit and the PCB, the FPC has a wiring pattern on one side and the other surface on the other side. PC
A semiconductor laser device comprising a solid ground surface connected to B and being disposed so as to surround the high frequency superposition unit. The width of the FPC is substantially equal to the width of the high frequency superposition unit, and
Has a blade portion for surrounding a side surface portion of the high frequency superposition unit. Further, the solid ground surface of the FPC and the high frequency superposition unit are soldered.

[0008]

According to the present invention, the electromagnetic wave leaked from the high frequency superimposing unit is absorbed by the solid ground surface formed on one surface of the FPC arranged so as to surround the high frequency superimposing unit, and the other electromagnetic wave is absorbed by the electromagnetic wave. The impact on the parts is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 7 shows an outline of an optical pickup in an optical disk device. In the figure, reference numeral 1 denotes a semiconductor laser, and a light flux from this semiconductor laser 1 is collimated by a collimator lens 21 and transmitted through a beam splitter 22 to an objective lens 23. Incident. Then, the objective lens 23 irradiates the information recording medium 24 as a minute spot. The reflected light from the information recording medium 24 becomes parallel light again by the objective lens 23, and the beam splitter 22
Is reflected downward in the figure and guided to the detection lens 25.
The light flux is again condensed by the detection lens 25, part of which is transmitted by the knife edge prism 26, is guided to the focusing error signal photodetector 27, and the rest is guided to the polarization beam splitter 28. The light guided to the polarization beam splitter 28 is separated into a P wave and an S wave, and on the other hand, is guided to a photodetector 29 for detecting a tracking error signal and the other to a detector 30 for detecting a reproduction signal. Here, the focusing error signal is detected by the known knife edge method, and the tracking error signal is detected by the known push-pull method. The reproduction signal is detected by the difference between the outputs from the tracking error signal detecting photodetector 29 and the reproduction signal detecting photodetector 30.

Here, due to the characteristics of the beam splitter 22, it is not possible to reflect 100% of the reflected light from the information recording medium 24 and guide it to the detection optical system. Therefore, returning light is generated in the semiconductor laser 1. When the return light is generated, the oscillation mode of the semiconductor laser 1 is disturbed and noise is generated in the output signal. As a method of suppressing this, it is common practice to pulse drive the semiconductor laser 1 at a high frequency to emit light in a multimode. The optimum frequency is given by the following equation. θ = 2π HF (2L / C) HF: Superposition frequency C: Speed of light L: Optical path length Since the noise increases just before θ is an integer multiple of 2π, select HF so that it does not occur within the required L range. .
The modulation factor is defined by the following equation. Modulation rate (%) = (DC optical output at high frequency superimposed current) /
(DC light output during non-modulation) × 100 Normally, the superposition frequency is several hundred MHz and the degree of modulation is several hundred%.
Becomes

By the way, when the above-mentioned high frequency superimposition is performed, a high frequency component is generated as an electromagnetic wave from the high frequency generating circuit, and this electromagnetic wave becomes noise and adversely affects other electric circuits and the like. The present invention relates to a semiconductor laser device in which the influence of electromagnetic waves is prevented, and its embodiment will be described below.

FIG. 1 shows a first embodiment according to the present invention, in which 1 is a semiconductor laser, which is a semiconductor laser 1.
Is attached to a high-frequency superposition unit 2 (in which the high-frequency superposition circuit is covered with a conductive shield plate) for pulse-driving the semiconductor laser 1 to emit light in a multimode. Then, one end of a flexible printed wiring board (hereinafter referred to as FPC) 3 is fixed to the connector pin 5 provided on the shield plate of the high frequency superposition unit 2 by soldering or the like. Has a width substantially equal to the width of the high frequency superposition unit 2, and is arranged in a shape surrounding the high frequency superposition unit 2, that is, in a substantially U shape, and the other end is connected to a PCB (printed wiring board) 4.
A semiconductor laser drive circuit and the like (not shown) are mounted on the PCB 4.

As shown in the cross-sectional explanatory view of FIG. 2, the FPC 3 has copper foils 3b and 3d laminated on both sides of a base film 3c, and the copper foils 3b and 3d are further contacted with the base film 3c. Is the cover film 3
a and 3e are laminated. Here, the copper foil 3b is the ground of the semiconductor laser drive circuit and the high frequency superposition unit 2
The copper ground plane is connected to the ground of
A wiring pattern connecting the semiconductor laser drive circuit and the high frequency superposition circuit unit 2 is formed in d. The solid ground surface side is arranged so as to face the high frequency superposition unit 2 side.

In the semiconductor laser device of this embodiment, the drive signal output from the semiconductor laser drive circuit mounted on the PCB 4 is transmitted to the high frequency superposition unit 2 by the wiring pattern formed on the copper foil 3d of the FPC 3. The semiconductor laser 1 is made to emit light. At this time, the leakage noise radiated from the high frequency superposition unit 2 is absorbed by the solid ground surface 3b of the FPC 3, and the noise is reduced.

FIG. 3 shows a second embodiment of the present invention. As with the first embodiment, the semiconductor laser 1 includes a high frequency superposition unit 2 (the high frequency superposition circuit is covered with a conductive shield plate). Attached to the connector plate 5 provided on the shield plate of the high frequency superposition unit 2, one end of the FPC 6 is fixed by soldering or the like.
The high-frequency superimposing unit 2 is arranged so as to surround the high-frequency superimposing unit 2, that is, substantially U-shaped, and the other end is connected to the PCB 4. A semiconductor laser drive circuit and the like are mounted on the electric board 4.

The FPC 6 has a laminated structure similar to that of the first embodiment, and further has a blade portion 7 as shown in FIG. 4, and the blade portion 7 is provided to the high frequency superposition unit 2 side. By being bent, it is arranged so as to cover the side surface portion of the high frequency superposition unit 2. Therefore, Example 1
Similarly, the leakage noise radiated from the high frequency superimposing unit 2 is absorbed by the solid land surface 3b of the FPC 3 to reduce the noise, and the noise leaking from the side surface of the high frequency superimposing unit 2 is also absorbed by the blade portion 7 to be reduced. can do.

FIGS. 5 and 6 show a third embodiment. As with the first embodiment, the semiconductor laser 1 includes a high frequency superposition unit 2 (the high frequency superposition circuit is covered with a conductive shield plate). Attached to the connector plate 5 provided on the shield plate of the high frequency superposition unit 2, one end of the FPC 8 is fixed by soldering or the like.
The high-frequency superimposing unit 2 is arranged so as to surround the high-frequency superimposing unit 2, that is, substantially U-shaped, and the other end is connected to the PCB 4. A semiconductor laser drive circuit and the like are mounted on the PCB 4.

As shown in FIG. 6, the FPC 8 has a blade portion 9, and further, a part of the solid land portion is solderable to the side surface portion of the high frequency superposition unit 2 and the solder land 10 is solderable.
have. Thereby, the ground of the shield plate of the high frequency superposition unit 2 is reinforced, and the high frequency superposition unit 2
Leakage noise radiated from can be reduced. Further, as in the second embodiment, noise can be absorbed by the solid ground surface of the FPC 8 and the blade portion 9, and the noise can be reduced.

[0019]

According to the present invention, the FPC connecting the high frequency superimposing unit and the printed wiring board (hereinafter referred to as PCB) is arranged so as to surround the high frequency superimposing unit.
The PC functions as a shield plate, and the noise radiated from the high frequency superposition unit can be increased without increasing the number of parts.
Can be reduced. Further, since the FPC connecting the high frequency superimposing unit and the PCB is arranged so as to also surround the side surface of the high frequency superimposing unit, noise radiated from the high frequency superimposing unit can be reduced without increasing the number of parts. it can. Further, since the FPC connecting the high frequency superimposing unit and the PCB is arranged so as to also surround the side surface of the high frequency superimposing unit, and the solid land of the FPC and the high frequency superimposing unit are connected by soldering or the like, It is possible to reduce the noise radiated from the device without increasing the number of parts.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view of an FPC.

FIG. 3 is a schematic explanatory view showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of an FPC used in a second embodiment of the present invention.

FIG. 5 is a schematic explanatory view showing a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of an FPC used in a third embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an outline of an optical pickup in an optical disc device.

[Explanation of symbols]

 1 Semiconductor Laser 2 High-Frequency Superposition Unit 3 FPC 4 PCB 5 Connector Pin 6 FPC 7 Blade 8 FPC 9 Blade 10 Solder Land 21 Collimator Lens 22 Beam Splitter 23 Objective Lens 24 Information Recording Medium 25 Detection Lens 26 Knife Edge Prism 27 Optical Detection 28 Polarizing beam splitter 29 Photodetector 30 Photodetector

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // G11B 7/09 A 9368-5D

Claims (4)

[Claims] 1. A semiconductor laser, a high frequency superposition unit for emitting the semiconductor laser at a high frequency, a PCB equipped with a drive circuit for driving the semiconductor laser and the high frequency superposition unit, the high frequency superposition unit and the PCB. In a semiconductor laser device comprising an FPC (flexible printed wiring board) for connecting the FPC (flexible printed wiring board), the FPC has a wiring pattern on one surface and a solid ground surface connected to the PCB, and surrounds the high frequency superposition unit. A semiconductor laser device characterized in that the semiconductor laser device is arranged as follows. 2. The semiconductor laser device according to claim 1, wherein the width of the FPC is substantially equal to the width of the high frequency superposition unit. 3. The semiconductor laser device according to claim 1, wherein the FPC has a blade portion for surrounding a side surface portion of the high frequency superposition unit. 4. The semiconductor laser device according to claim 3, wherein the solid ground surface of the FPC and the high-frequency superposition unit are soldered.